期刊
SURFACE SCIENCE
卷 630, 期 -, 页码 187-194出版社
ELSEVIER
DOI: 10.1016/j.susc.2014.08.012
关键词
Autocatalytic desorption; Island fragmentation; Chemisorbed oxygen; Molecular desorption; Hot atoms
资金
- US Department of Energy, Office of Basic Energy Sciences, Catalysis Science Program [DE-FG02-84-ER13289]
- National Science Foundation, Division of Chemistry, Analytical and Surface Science [CHE-0952790]
- Alexander von Humboldt Foundation
The interplay between thermal desorption of chemisorbed dioxygen and its dissociation was studied with temperature programmed methods. Analysis of the kinetics of molecular desorption and the fraction of adsorbed molecules which dissociate is consistent with a model in which oxygen atoms released by the dissociation event induce desorption of the molecular species. These unequilibrated atoms exhibit a mean free path relative to the chemisorbed dioxygen of 1.8 nm prior to thermalization with the surface, displacing chemisorbed dioxygen within their reach. Each dissociation event leads to desorption of two oxygen molecules if the space between chemisorbed molecules approaches the minimum of 0.58 nm. This condition can be achieved experimentally by saturating the population of chemisorbed dioxygen (0.33 ML O-2) at 90-100 K. Oxygen adatoms recombine near 580 K from the reconstructed (n x 1)-O adlayer with kinetics dictated by progressive fragmentation of the O(AgO)(m) rows. This behavior gives rise to autocatalytic recombination kinetics of oxygen adatoms which produces both an acceleration of rate at constant temperature and unusual recombination kinetics in temperature programmed desorption. (C) 2014 Elsevier B.V. All rights reserved.
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